What was done
The authors grew rice (Oryza sativa L. cv. Mutsu-homare) plants hydroponically in controlled environment chambers having atmospheric CO2 concentrations of 350 and 700 ppm and day/night air temperatures of 24/17 (ambient) and 26/19°C (elevated) to study the interactive effects of elevated CO2 and temperature on growth in this important agricultural crop.

What was learned
After 18 weeks of treatment exposure, the authors reported that elevated CO2 had no effect on whole-plant biomass at ambient growth temperatures.  However, with an additional 2°C of warming, atmospheric CO2 enrichment produced a whole-plant biomass enhancement of 22%.  These results are different from those of Ziska et al. (1997), who reported significant CO2-induced growth enhancements at ambient but not elevated air temperature.

What it means
As the atmospheric CO2 concentration continues to rise, this rice cultivar will probably not exhibit any significant increase in biomass production, unless there is a concomitant increase in ambient air temperature.  In comparing this result with that obtained by Ziska et al. (1997), one realizes the importance of screening agricultural cultivars for CO2-sensitivity prior to planting in order to maximize potential crop yields under future CO2-enriched atmospheres.

References
Ziska, L.H., Namuco, O., Moya, T. and Quilang, J.  1997.  Growth and yield response of field-grown tropical rice to increasing carbon dioxide and air temperature.  Agronomy Journal 89: 45-53.